Do you already have a plan of where you want to put lights and outlets?
If not, you should cancel the Wednesday appointment with the electrician and spend some time drawing up plans, unless your electrician is also a lighting designer.
I would use 12 gauge wire for the speakers. The total length of the run including the portion in the wall (home wiring cable such as Romex works nicely) and the portions outside the walls going to the amp and speakers may well exceed 30 feet.
Running wire throughoug the house may work out for you but somehow I would not bother with that. Too often someone may want to watch something in the theater while you want to watch or listen to something else in a different room and one shared sound system down in the theater can't do that.
Component cables -- A set of three RCA plug 75 ohm cables.
Home theater hints:
Constructing a Basement Home Theater